Rabbits and guinea pigs are being immunized with saline extracts of colon obtained from rabbits, guinea pigs and germ free rats. The role of circulating anti-colon antibody and sensitized lymphocytes in producing inflammatory and ulcerative changes in the colon of the immunized animal is under investigation. Animals immunized with colon from a heterologous species produce antibody to intestine specific antigens of that species. However immunizing an animal with a colon extract of the homologous species only leads to antibody production to non-tissue specific antigen. Approximately 50% of the immunized animals develop inflammatory bowel changes. The mechanism by which sensitized lymphocytes mediate these changes is being sought. Both non-specific cellular immune reactions and cellular immune reactions to intestinal antigens are being investigated as factors in the disease process. BIBLIOGRAPHIC REFERENCE: Rabin, B.S. Duodenum, Ileum and Colon Specific Antigens. Int. Arch. All. and Appl. Immunol. 50:133, 1976.